A terahertz wave band (0.1 THz to 10 THz) transmits a non-metallic material and a non-conductive material and has an electromagnetic wave of very low energy as much as several meV and therefore little affects a human body.
An example of the typical non-contact method for measuring a thickness of non-metallic material may include an optical method, which may not measure a thickness of material through which light is not transmitted. On the other hand, the terahertz wave may transmit the non-metallic material, and therefore a method for measuring a thickness of a non-metallic material through which light is not transmitted may use a terahertz wave.
Further, a resonance frequency of very various molecules is distributed in the terahertz wave band. In this case, these molecules are identified in real-time by a non-destructive, non-opened, non-contact method. As a result, it is expected that a new-conceptual analysis technology which does not exist now in medical treatment, medical science, agricultural food, environmental measurement, bio, advanced material evaluation, etc., may be implemented.
Therefore, researches to develop and use wave sources operated in a frequency band of 0.1 to 10 THz which is called a THz gap region have been conducted.
As the related art document disclosing a method for generating a terahertz continuous wave of which the frequency is changed at a high speed using a wavelength-fixed laser and a wavelength-swept laser, there is Korean Patent No. 10-1453472.
However, the method suggests only a technology of merely generating a terahertz wave but does not suggest a technology of measuring a thickness of a sample using the generated terahertz wave.